Polyester resins such as polyethylene terephthalate, polymethylene terephthalate, polyethylene naphthalate, polylactic acid, and the like are excellent in heat resistance, chemical resistance, dynamic characteristics, electric characteristics, and the like and also excellent in cost and performance, and are thus widely used as fibers and films in the industrial field. Further, the polyester resins are excellent in gas barrier property, sanitary property, and transparency and are thus widely used for beverage bottles, cosmetic and pharmaceutical containers, detergent and shampoo containers, and the like.
However, polyester resins generally have extremely low crystallization rates in spite of being crystalline resins, and thus have a very narrow range of molding conditions and difficulty in improving a processing cycle. Therefore, use as molding materials is still restricted. Further, molded products prepared by molding polyester resins have low heat distortion temperatures, and thus there is the problem of limiting operating temperatures.
A generally known method for improving the crystallization rates of polyester resins includes adding a nucleator. Such nucleators include a mineral, an organic acid metal salt, an inorganic salt, a metal oxide, or the like. General-purpose compounds used as the nucleator include metal salts, such as sodium benzoate, aluminum p-tert-butylbenzoate, aromatic phosphate metal salts, and the like; and compounds such as dibenzylidene sorbitol and the like.
Further, there is known a method of adding a resin oligomer for improving mobility at a resin processing temperature. For example, Patent Document 1 proposes a method of adding a metal salt of an abietic acid compound in order to promote the crystallization rate of a polyester resin. Patent Document 2 discloses a method of adding 4-aminobenzenesulfonamide to an olefin resin. Patent Document 3 proposes a method of adding a phosphate metal salt and an aliphatic carboxylic acid metal salt to a crystalline polymer.
Patent Document 4 proposes a method using a transition metal salt of a carboxylic acid as a nucleator for a composition containing polyethylene terephthalate and polyethylene naphthalate. Patent Document 5 proposes a method of obtaining a polyester resin composition by using an alkylene bis fatty acid amide and a quinacridone as a nucleator.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 08-059968    Patent Document 2: U.S. Pat. No. 3,756,997    Patent Document 3: Japanese Unexamined Patent Application Publication No. 2005-162867    Patent Document 4: Japanese Unexamined Patent Application Publication (translation of PCT Application) No. 2002-507955    Patent Document 5: Japanese Unexamined Patent Application Publication No. 2006-113473